diff --git a/extensions/vscode-api-tests/package.json b/extensions/vscode-api-tests/package.json
index c4dd03bdfc7..ebe29bc3836 100644
--- a/extensions/vscode-api-tests/package.json
+++ b/extensions/vscode-api-tests/package.json
@@ -44,7 +44,8 @@
     "treeItemCheckbox",
     "treeViewReveal",
     "workspaceTrust",
-    "telemetry"
+    "telemetry",
+    "localization"
   ],
   "private": true,
   "activationEvents": [],
diff --git a/src/vs/platform/extensions/common/extensions.ts b/src/vs/platform/extensions/common/extensions.ts
index 9296a375d9c..011d3fbee14 100644
--- a/src/vs/platform/extensions/common/extensions.ts
+++ b/src/vs/platform/extensions/common/extensions.ts
@@ -268,6 +268,7 @@ export interface IRelaxedExtensionManifest {
 	description?: string;
 	main?: string;
 	browser?: string;
+	l10nBundleLocation?: string;
 	icon?: string;
 	categories?: string[];
 	keywords?: string[];
diff --git a/src/vs/workbench/api/browser/extensionHost.contribution.ts b/src/vs/workbench/api/browser/extensionHost.contribution.ts
index 2832cd5c9f2..203f680485c 100644
--- a/src/vs/workbench/api/browser/extensionHost.contribution.ts
+++ b/src/vs/workbench/api/browser/extensionHost.contribution.ts
@@ -16,6 +16,7 @@ import { TokenClassificationExtensionPoints } from 'vs/workbench/services/themes
 import { LanguageConfigurationFileHandler } from 'vs/workbench/contrib/codeEditor/browser/languageConfigurationExtensionPoint';
 
 // --- mainThread participants
+import './mainThreadLocalization';
 import './mainThreadBulkEdits';
 import './mainThreadCodeInsets';
 import './mainThreadCLICommands';
diff --git a/src/vs/workbench/api/browser/mainThreadLocalization.ts b/src/vs/workbench/api/browser/mainThreadLocalization.ts
new file mode 100644
index 00000000000..988fb8ba6c3
--- /dev/null
+++ b/src/vs/workbench/api/browser/mainThreadLocalization.ts
@@ -0,0 +1,26 @@
+/*---------------------------------------------------------------------------------------------
+ *  Copyright (c) Microsoft Corporation. All rights reserved.
+ *  Licensed under the MIT License. See License.txt in the project root for license information.
+ *--------------------------------------------------------------------------------------------*/
+
+import { MainContext, MainThreadLocalizationShape } from 'vs/workbench/api/common/extHost.protocol';
+import { extHostNamedCustomer, IExtHostContext } from 'vs/workbench/services/extensions/common/extHostCustomers';
+import { URI, UriComponents } from 'vs/base/common/uri';
+import { IFileService } from 'vs/platform/files/common/files';
+import { Disposable } from 'vs/base/common/lifecycle';
+
+@extHostNamedCustomer(MainContext.MainThreadLocalization)
+export class MainThreadLocalization extends Disposable implements MainThreadLocalizationShape {
+
+	constructor(
+		extHostContext: IExtHostContext,
+		@IFileService private readonly fileService: IFileService,
+	) {
+		super();
+	}
+
+	async $fetchBundleContents(uriComponents: UriComponents): Promise<string> {
+		const contents = await this.fileService.readFile(URI.revive(uriComponents));
+		return contents.value.toString();
+	}
+}
diff --git a/src/vs/workbench/api/common/extHost.api.impl.ts b/src/vs/workbench/api/common/extHost.api.impl.ts
index 8fadafd3118..3b49d968ab8 100644
--- a/src/vs/workbench/api/common/extHost.api.impl.ts
+++ b/src/vs/workbench/api/common/extHost.api.impl.ts
@@ -93,6 +93,7 @@ import { combinedDisposable } from 'vs/base/common/lifecycle';
 import { checkProposedApiEnabled, ExtensionIdentifierSet, isProposedApiEnabled } from 'vs/workbench/services/extensions/common/extensions';
 import { DebugConfigurationProviderTriggerKind } from 'vs/workbench/contrib/debug/common/debug';
 import { IExtHostTelemetryLogService } from 'vs/workbench/api/common/extHostTelemetryLogService';
+import { IExtHostLocalizationService } from 'vs/workbench/api/common/extHostLocalizationService';
 
 export interface IExtensionRegistries {
 	mine: ExtensionDescriptionRegistry;
@@ -151,6 +152,7 @@ export function createApiFactoryAndRegisterActors(accessor: ServicesAccessor): I
 	const extHostSearch = rpcProtocol.set(ExtHostContext.ExtHostSearch, accessor.get(IExtHostSearch));
 	const extHostTask = rpcProtocol.set(ExtHostContext.ExtHostTask, accessor.get(IExtHostTask));
 	const extHostOutputService = rpcProtocol.set(ExtHostContext.ExtHostOutputService, accessor.get(IExtHostOutputService));
+	const extHostLocalization = rpcProtocol.set(ExtHostContext.ExtHostLocalization, accessor.get(IExtHostLocalizationService));
 
 	// manually create and register addressable instances
 	const extHostUrls = rpcProtocol.set(ExtHostContext.ExtHostUrls, new ExtHostUrls(rpcProtocol));
@@ -1167,6 +1169,28 @@ export function createApiFactoryAndRegisterActors(accessor: ServicesAccessor): I
 			}
 		};
 
+		// namespace: l10n
+		const l10n: typeof vscode.l10n = {
+			t(...params: [message: string, ...args: string[]] | [{ message: string; args: string[]; comment: string[] }]): string {
+				checkProposedApiEnabled(extension, 'localization');
+
+				if (typeof params[0] === 'string') {
+					const key = params.shift() as string;
+					return extHostLocalization.getMessage(extension.identifier.value, { message: key, args: params as string[] });
+				}
+
+				return extHostLocalization.getMessage(extension.identifier.value, params[0]);
+			},
+			get bundle() {
+				checkProposedApiEnabled(extension, 'localization');
+				return extHostLocalization.getBundle(extension.identifier.value);
+			},
+			get uri() {
+				checkProposedApiEnabled(extension, 'localization');
+				return extHostLocalization.getBundleUri(extension.identifier.value);
+			}
+		};
+
 		return <typeof vscode>{
 			version: initData.version,
 			// namespaces
@@ -1176,6 +1200,7 @@ export function createApiFactoryAndRegisterActors(accessor: ServicesAccessor): I
 			debug,
 			env,
 			extensions,
+			l10n,
 			languages,
 			notebooks,
 			scm,
diff --git a/src/vs/workbench/api/common/extHost.common.services.ts b/src/vs/workbench/api/common/extHost.common.services.ts
index 45ccc2baf3b..4658a622298 100644
--- a/src/vs/workbench/api/common/extHost.common.services.ts
+++ b/src/vs/workbench/api/common/extHost.common.services.ts
@@ -28,7 +28,9 @@ import { ILoggerService, ILogService } from 'vs/platform/log/common/log';
 import { ExtHostLogService } from 'vs/workbench/api/common/extHostLogService';
 import { ExtHostVariableResolverProviderService, IExtHostVariableResolverProvider } from 'vs/workbench/api/common/extHostVariableResolverService';
 import { ExtHostTelemetryLogService, IExtHostTelemetryLogService } from 'vs/workbench/api/common/extHostTelemetryLogService';
+import { ExtHostLocalizationService, IExtHostLocalizationService } from 'vs/workbench/api/common/extHostLocalizationService';
 
+registerSingleton(IExtHostLocalizationService, ExtHostLocalizationService, true);
 registerSingleton(ILoggerService, ExtHostLoggerService, true);
 registerSingleton(ILogService, ExtHostLogService, true);
 registerSingleton(IExtHostApiDeprecationService, ExtHostApiDeprecationService, false);
diff --git a/src/vs/workbench/api/common/extHost.protocol.ts b/src/vs/workbench/api/common/extHost.protocol.ts
index d355265276e..f4532aa46a7 100644
--- a/src/vs/workbench/api/common/extHost.protocol.ts
+++ b/src/vs/workbench/api/common/extHost.protocol.ts
@@ -2144,6 +2144,10 @@ export interface ExtHostThemingShape {
 export interface MainThreadThemingShape extends IDisposable {
 }
 
+export interface MainThreadLocalizationShape extends IDisposable {
+	$fetchBundleContents(uriComponents: UriComponents): Promise<string>;
+}
+
 export interface TunnelDto {
 	remoteAddress: { port: number; host: string };
 	localAddress: { port: number; host: string } | string;
@@ -2193,6 +2197,19 @@ export interface ExtHostTestingShape {
 	$refreshTests(controllerId: string, token: CancellationToken): Promise<void>;
 }
 
+export interface ExtHostLocalizationShape {
+	getMessage(extensionId: string, details: IStringDetails): string;
+	getBundle(extensionId: string): { [key: string]: string };
+	getBundleUri(extensionId: string): URI | undefined;
+	initializeLocalizedMessages(extension: IExtensionDescription): Promise<void>;
+}
+
+export interface IStringDetails {
+	message: string;
+	args?: string[];
+	comment?: string[];
+}
+
 export interface ITestControllerPatch {
 	label?: string;
 	canRefresh?: boolean;
@@ -2310,6 +2327,7 @@ export const MainContext = {
 	MainThreadTunnelService: createProxyIdentifier<MainThreadTunnelServiceShape>('MainThreadTunnelService'),
 	MainThreadTimeline: createProxyIdentifier<MainThreadTimelineShape>('MainThreadTimeline'),
 	MainThreadTesting: createProxyIdentifier<MainThreadTestingShape>('MainThreadTesting'),
+	MainThreadLocalization: createProxyIdentifier<MainThreadLocalizationShape>('MainThreadLocalizationShape')
 };
 
 export const ExtHostContext = {
@@ -2364,4 +2382,5 @@ export const ExtHostContext = {
 	ExtHostTimeline: createProxyIdentifier<ExtHostTimelineShape>('ExtHostTimeline'),
 	ExtHostTesting: createProxyIdentifier<ExtHostTestingShape>('ExtHostTesting'),
 	ExtHostTelemetry: createProxyIdentifier<ExtHostTelemetryShape>('ExtHostTelemetry'),
+	ExtHostLocalization: createProxyIdentifier<ExtHostLocalizationShape>('ExtHostLocalization'),
 };
diff --git a/src/vs/workbench/api/common/extHostExtensionService.ts b/src/vs/workbench/api/common/extHostExtensionService.ts
index 2f1bb393282..63f37f89625 100644
--- a/src/vs/workbench/api/common/extHostExtensionService.ts
+++ b/src/vs/workbench/api/common/extHostExtensionService.ts
@@ -40,6 +40,7 @@ import { ExtHostSecretState, IExtHostSecretState } from 'vs/workbench/api/common
 import { ExtensionSecrets } from 'vs/workbench/api/common/extHostSecrets';
 import { Schemas } from 'vs/base/common/network';
 import { IResolveAuthorityResult } from 'vs/workbench/services/extensions/common/extensionHostProxy';
+import { IExtHostLocalizationService } from 'vs/workbench/api/common/extHostLocalizationService';
 
 interface ITestRunner {
 	/** Old test runner API, as exported from `vscode/lib/testrunner` */
@@ -90,6 +91,7 @@ export abstract class AbstractExtHostExtensionService extends Disposable impleme
 	protected readonly _logService: ILogService;
 	protected readonly _extHostTunnelService: IExtHostTunnelService;
 	protected readonly _extHostTerminalService: IExtHostTerminalService;
+	protected readonly _extHostLocalizationService: IExtHostLocalizationService;
 
 	protected readonly _mainThreadWorkspaceProxy: MainThreadWorkspaceShape;
 	protected readonly _mainThreadTelemetryProxy: MainThreadTelemetryShape;
@@ -125,6 +127,7 @@ export abstract class AbstractExtHostExtensionService extends Disposable impleme
 		@IExtensionStoragePaths storagePath: IExtensionStoragePaths,
 		@IExtHostTunnelService extHostTunnelService: IExtHostTunnelService,
 		@IExtHostTerminalService extHostTerminalService: IExtHostTerminalService,
+		@IExtHostLocalizationService extHostLocalizationService: IExtHostLocalizationService
 	) {
 		super();
 		this._hostUtils = hostUtils;
@@ -136,6 +139,7 @@ export abstract class AbstractExtHostExtensionService extends Disposable impleme
 		this._logService = logService;
 		this._extHostTunnelService = extHostTunnelService;
 		this._extHostTerminalService = extHostTerminalService;
+		this._extHostLocalizationService = extHostLocalizationService;
 
 		this._mainThreadWorkspaceProxy = this._extHostContext.getProxy(MainContext.MainThreadWorkspace);
 		this._mainThreadTelemetryProxy = this._extHostContext.getProxy(MainContext.MainThreadTelemetry);
diff --git a/src/vs/workbench/api/common/extHostLocalizationService.ts b/src/vs/workbench/api/common/extHostLocalizationService.ts
new file mode 100644
index 00000000000..c09eccb0077
--- /dev/null
+++ b/src/vs/workbench/api/common/extHostLocalizationService.ts
@@ -0,0 +1,104 @@
+/*---------------------------------------------------------------------------------------------
+ *  Copyright (c) Microsoft Corporation. All rights reserved.
+ *  Licensed under the MIT License. See License.txt in the project root for license information.
+ *--------------------------------------------------------------------------------------------*/
+
+import { Language } from 'vs/base/common/platform';
+import { format } from 'vs/base/common/strings';
+import { URI } from 'vs/base/common/uri';
+import { IExtensionDescription } from 'vs/platform/extensions/common/extensions';
+import { createDecorator } from 'vs/platform/instantiation/common/instantiation';
+import { ILogService } from 'vs/platform/log/common/log';
+import { ExtHostLocalizationShape, IStringDetails, MainContext, MainThreadLocalizationShape } from 'vs/workbench/api/common/extHost.protocol';
+import { IExtHostRpcService } from 'vs/workbench/api/common/extHostRpcService';
+
+export class ExtHostLocalizationService implements ExtHostLocalizationShape {
+	readonly _serviceBrand: undefined;
+
+	private readonly _proxy: MainThreadLocalizationShape;
+
+	private readonly bundleCache: Map<string, { contents: { [key: string]: string }; uri: URI }> = new Map();
+
+	constructor(
+		@IExtHostRpcService rpc: IExtHostRpcService,
+		@ILogService private readonly logService: ILogService
+	) {
+		this._proxy = rpc.getProxy(MainContext.MainThreadLocalization);
+	}
+
+	getMessage(extensionId: string, details: IStringDetails): string {
+		const { message, args, comment } = details;
+		if (Language.isDefault()) {
+			return format(message, args);
+		}
+
+		let key = message;
+		if (comment && comment.length > 0) {
+			key += `/${comment.join()}`;
+		}
+		const str = this.bundleCache.get(extensionId)?.contents[key];
+		if (!str) {
+			this.logService.warn(`Using default string since no string found in i18n bundle that has the key: ${key}`);
+		}
+		return format(str ?? key, args);
+	}
+
+	getBundle(extensionId: string): { [key: string]: string } {
+		return this.bundleCache.get(extensionId)?.contents ?? {};
+	}
+
+	getBundleUri(extensionId: string): URI | undefined {
+		return this.bundleCache.get(extensionId)?.uri;
+	}
+
+	async initializeLocalizedMessages(extension: IExtensionDescription): Promise<void> {
+		if (Language.isDefault()
+			// TODO: support builtin extensions
+			|| !extension.l10nBundleLocation
+		) {
+			return;
+		}
+
+		if (this.bundleCache.has(extension.identifier.value)) {
+			return;
+		}
+
+		let contents: { [key: string]: string } | undefined;
+		const bundleLocation = this.getBundleLocation(extension);
+		if (!bundleLocation) {
+			this.logService.error(`No bundle location found for extension ${extension.identifier.value}`);
+			return;
+		}
+		const bundleUri = URI.joinPath(bundleLocation, `bundle.l10n.${Language.value()}.json`);
+
+		try {
+			const response = await this._proxy.$fetchBundleContents(bundleUri);
+			contents = JSON.parse(response);
+		} catch (e) {
+			this.logService.error(`Failed to load translations for ${extension.identifier.value} from ${bundleUri}: ${e.message}`);
+			return;
+		}
+
+		if (contents) {
+			this.bundleCache.set(extension.identifier.value, {
+				contents,
+				uri: bundleUri
+			});
+		}
+	}
+
+	private getBundleLocation(extension: IExtensionDescription): URI | undefined {
+		// TODO: support builtin extensions using IExtHostInitDataService
+		// if (extension.isBuiltin && this.initData.nlsBaseUrl) {
+		// 	return URI.joinPath(this.initData.nlsBaseUrl, extension.identifier.value, 'main');
+		// }
+
+		if (extension.l10nBundleLocation) {
+			return URI.joinPath(extension.extensionLocation, extension.l10nBundleLocation);
+		}
+		return undefined;
+	}
+}
+
+export const IExtHostLocalizationService = createDecorator<IExtHostLocalizationService>('IExtHostLocalizationService');
+export interface IExtHostLocalizationService extends ExtHostLocalizationService { }
diff --git a/src/vs/workbench/api/common/extensionHostMain.ts b/src/vs/workbench/api/common/extensionHostMain.ts
index 6328360e0b3..a204a569f0e 100644
--- a/src/vs/workbench/api/common/extensionHostMain.ts
+++ b/src/vs/workbench/api/common/extensionHostMain.ts
@@ -136,6 +136,7 @@ export class ExtensionHostMain {
 		initData.environment.extensionTestsLocationURI = URI.revive(rpcProtocol.transformIncomingURIs(initData.environment.extensionTestsLocationURI));
 		initData.environment.globalStorageHome = URI.revive(rpcProtocol.transformIncomingURIs(initData.environment.globalStorageHome));
 		initData.environment.workspaceStorageHome = URI.revive(rpcProtocol.transformIncomingURIs(initData.environment.workspaceStorageHome));
+		initData.nlsBaseUrl = URI.revive(rpcProtocol.transformIncomingURIs(initData.nlsBaseUrl));
 		initData.logsLocation = URI.revive(rpcProtocol.transformIncomingURIs(initData.logsLocation));
 		initData.logFile = URI.revive(rpcProtocol.transformIncomingURIs(initData.logFile));
 		initData.workspace = rpcProtocol.transformIncomingURIs(initData.workspace);
diff --git a/src/vs/workbench/api/node/extHostExtensionService.ts b/src/vs/workbench/api/node/extHostExtensionService.ts
index c15b76ff78d..32e4f223aad 100644
--- a/src/vs/workbench/api/node/extHostExtensionService.ts
+++ b/src/vs/workbench/api/node/extHostExtensionService.ts
@@ -89,7 +89,7 @@ export class ExtHostExtensionService extends AbstractExtHostExtensionService {
 		return extensionDescription.main;
 	}
 
-	protected _loadCommonJSModule<T>(extension: IExtensionDescription | null, module: URI, activationTimesBuilder: ExtensionActivationTimesBuilder): Promise<T> {
+	protected async _loadCommonJSModule<T>(extension: IExtensionDescription | null, module: URI, activationTimesBuilder: ExtensionActivationTimesBuilder): Promise<T> {
 		if (module.scheme !== Schemas.file) {
 			throw new Error(`Cannot load URI: '${module}', must be of file-scheme`);
 		}
@@ -98,20 +98,21 @@ export class ExtHostExtensionService extends AbstractExtHostExtensionService {
 		this._logService.trace(`ExtensionService#loadCommonJSModule ${module.toString(true)}`);
 		this._logService.flush();
 		const extensionId = extension?.identifier.value;
+		if (extension) {
+			await this._extHostLocalizationService.initializeLocalizedMessages(extension);
+		}
 		try {
 			if (extensionId) {
 				performance.mark(`code/extHost/willLoadExtensionCode/${extensionId}`);
 			}
 			r = require.__$__nodeRequire<T>(module.fsPath);
-		} catch (e) {
-			return Promise.reject(e);
 		} finally {
 			if (extensionId) {
 				performance.mark(`code/extHost/didLoadExtensionCode/${extensionId}`);
 			}
 			activationTimesBuilder.codeLoadingStop();
 		}
-		return Promise.resolve(r);
+		return r;
 	}
 
 	public async $setRemoteEnvironment(env: { [key: string]: string | null }): Promise<void> {
diff --git a/src/vs/workbench/api/worker/extHostExtensionService.ts b/src/vs/workbench/api/worker/extHostExtensionService.ts
index aceb7ba278a..28b24d42950 100644
--- a/src/vs/workbench/api/worker/extHostExtensionService.ts
+++ b/src/vs/workbench/api/worker/extHostExtensionService.ts
@@ -12,7 +12,6 @@ import { IExtensionDescription } from 'vs/platform/extensions/common/extensions'
 import { ExtensionRuntime } from 'vs/workbench/api/common/extHostTypes';
 import { timeout } from 'vs/base/common/async';
 import { ExtHostConsoleForwarder } from 'vs/workbench/api/worker/extHostConsoleForwarder';
-import { Language } from 'vs/base/common/platform';
 
 class WorkerRequireInterceptor extends RequireInterceptor {
 
@@ -96,17 +95,14 @@ export class ExtHostExtensionService extends AbstractExtHostExtensionService {
 			throw err;
 		}
 
-		const strings: { [key: string]: string[] } = await this.fetchTranslatedStrings(extension);
+		if (extension) {
+			await this._extHostLocalizationService.initializeLocalizedMessages(extension);
+		}
 
 		// define commonjs globals: `module`, `exports`, and `require`
 		const _exports = {};
 		const _module = { exports: _exports };
 		const _require = (request: string) => {
-			// In order to keep vscode-nls synchronous, we prefetched the translations above
-			// and then return them here when the extension is loaded.
-			if (request === 'vscode-nls-web-data') {
-				return strings;
-			}
 			const result = this._fakeModules!.getModule(request, module);
 			if (result === undefined) {
 				throw new Error(`Cannot load module '${request}'`);
@@ -144,44 +140,6 @@ export class ExtHostExtensionService extends AbstractExtHostExtensionService {
 			await timeout(10);
 		}
 	}
-
-	private async fetchTranslatedStrings(extension: IExtensionDescription | null): Promise<{ [key: string]: string[] }> {
-		let strings: { [key: string]: string[] } = {};
-		if (!extension) {
-			return {};
-		}
-		const translationsUri = Language.isDefaultVariant()
-			// If we are in the default variant, load the translations for en only.
-			? extension.browserNlsBundleUris?.en
-			// Otherwise load the translations for the current locale with English as a fallback.
-			: extension.browserNlsBundleUris?.[Language.value()] ?? extension.browserNlsBundleUris?.en;
-		if (extension && translationsUri) {
-			try {
-				const response = await fetch(translationsUri.toString(true));
-				if (!response.ok) {
-					throw new Error(await response.text());
-				}
-				strings = await response.json();
-			} catch (e) {
-				try {
-					console.error(`Failed to load translations for ${extension.identifier.value} from ${translationsUri}: ${e.message}`);
-					const englishStrings = extension.browserNlsBundleUris?.en;
-					if (englishStrings) {
-						const response = await fetch(englishStrings.toString(true));
-						if (!response.ok) {
-							throw new Error(await response.text());
-						}
-						strings = await response.json();
-					}
-					throw new Error('No English strings found');
-				} catch (e) {
-					// TODO what should this do? We really shouldn't ever be here...
-					console.error(e);
-				}
-			}
-		}
-		return strings;
-	}
 }
 
 function ensureSuffix(path: string, suffix: string): string {
diff --git a/src/vs/workbench/services/extensions/browser/webWorkerExtensionHost.ts b/src/vs/workbench/services/extensions/browser/webWorkerExtensionHost.ts
index eb70bb9ff17..2c35ebcfaa6 100644
--- a/src/vs/workbench/services/extensions/browser/webWorkerExtensionHost.ts
+++ b/src/vs/workbench/services/extensions/browser/webWorkerExtensionHost.ts
@@ -277,6 +277,12 @@ export class WebWorkerExtensionHost extends Disposable implements IExtensionHost
 		const [telemetryInfo, initData] = await Promise.all([this._telemetryService.getTelemetryInfo(), this._initDataProvider.getInitData()]);
 		const workspace = this._contextService.getWorkspace();
 		const deltaExtensions = this.extensions.set(initData.allExtensions, initData.myExtensions);
+		const nlsBaseUrl = this._productService.extensionsGallery?.nlsBaseUrl;
+		let nlsUrlWithDetails: URI | undefined = undefined;
+		// Only use the nlsBaseUrl if we are using a language other than the default, English.
+		if (nlsBaseUrl && this._productService.commit && !platform.Language.isDefaultVariant()) {
+			nlsUrlWithDetails = URI.joinPath(URI.parse(nlsBaseUrl), this._productService.commit, this._productService.version, platform.Language.value());
+		}
 		return {
 			commit: this._productService.commit,
 			version: this._productService.version,
@@ -304,6 +310,7 @@ export class WebWorkerExtensionHost extends Disposable implements IExtensionHost
 			},
 			allExtensions: deltaExtensions.toAdd,
 			myExtensions: deltaExtensions.myToAdd,
+			nlsBaseUrl: nlsUrlWithDetails,
 			telemetryInfo,
 			logLevel: this._logService.getLevel(),
 			logsLocation: this._extensionHostLogsLocation,
diff --git a/src/vs/workbench/services/extensions/common/extensionHostProtocol.ts b/src/vs/workbench/services/extensions/common/extensionHostProtocol.ts
index 285ab4355c2..0f5865d1100 100644
--- a/src/vs/workbench/services/extensions/common/extensionHostProtocol.ts
+++ b/src/vs/workbench/services/extensions/common/extensionHostProtocol.ts
@@ -28,6 +28,7 @@ export interface IExtensionHostInitData {
 	workspace?: IStaticWorkspaceData | null;
 	allExtensions: IExtensionDescription[];
 	myExtensions: ExtensionIdentifier[];
+	nlsBaseUrl?: URI;
 	telemetryInfo: ITelemetryInfo;
 	logLevel: LogLevel;
 	logsLocation: URI;
diff --git a/src/vs/workbench/services/extensions/common/extensionsApiProposals.ts b/src/vs/workbench/services/extensions/common/extensionsApiProposals.ts
index 6d0b33157b9..cd7b1c8b8f2 100644
--- a/src/vs/workbench/services/extensions/common/extensionsApiProposals.ts
+++ b/src/vs/workbench/services/extensions/common/extensionsApiProposals.ts
@@ -37,6 +37,7 @@ export const allApiProposals = Object.freeze({
 	inlineCompletionsNew: 'https://raw.githubusercontent.com/microsoft/vscode/main/src/vscode-dts/vscode.proposed.inlineCompletionsNew.d.ts',
 	interactiveWindow: 'https://raw.githubusercontent.com/microsoft/vscode/main/src/vscode-dts/vscode.proposed.interactiveWindow.d.ts',
 	ipc: 'https://raw.githubusercontent.com/microsoft/vscode/main/src/vscode-dts/vscode.proposed.ipc.d.ts',
+	localization: 'https://raw.githubusercontent.com/microsoft/vscode/main/src/vscode-dts/vscode.proposed.localization.d.ts',
 	notebookCellExecutionState: 'https://raw.githubusercontent.com/microsoft/vscode/main/src/vscode-dts/vscode.proposed.notebookCellExecutionState.d.ts',
 	notebookContentProvider: 'https://raw.githubusercontent.com/microsoft/vscode/main/src/vscode-dts/vscode.proposed.notebookContentProvider.d.ts',
 	notebookControllerKind: 'https://raw.githubusercontent.com/microsoft/vscode/main/src/vscode-dts/vscode.proposed.notebookControllerKind.d.ts',
diff --git a/src/vscode-dts/vscode.proposed.localization.d.ts b/src/vscode-dts/vscode.proposed.localization.d.ts
new file mode 100644
index 00000000000..538dc68d108
--- /dev/null
+++ b/src/vscode-dts/vscode.proposed.localization.d.ts
@@ -0,0 +1,25 @@
+/*---------------------------------------------------------------------------------------------
+ *  Copyright (c) Microsoft Corporation. All rights reserved.
+ *  Licensed under the MIT License. See License.txt in the project root for license information.
+ *--------------------------------------------------------------------------------------------*/
+
+declare module 'vscode' {
+	export namespace l10n {
+		/**
+		 * A string that can be pulled out of a localization bundle if it exists.
+		 */
+		export function t(message: string, ...args: string[]): string;
+		/**
+		 * A string that can be pulled out of a localization bundle if it exists.
+		 */
+		export function t(options: { message: string; args: string[]; comment: string[] }): string;
+		/**
+		 * The bundle of localized strings that have been loaded for the extension.
+		 */
+		export const bundle: { [key: string]: string };
+		/**
+		 * The URI of the localization bundle that has been loaded for the extension.
+		 */
+		export const uri: Uri | undefined;
+	}
+}